using System;
using System.Buffers;
using System.Collections.Concurrent;
using Unity.Mathematics;
using System.Collections.Generic;

namespace Net.BITKit.Quadtree
{
    public struct QuadtreeNode
    {
        public readonly Quadtree Root;
        
        public float2 Center; // 节点中心
        public float2 Size;   // 节点大小

        public readonly QuadtreeNode[] Children; // 子节点
        public readonly HashSet<int> Objects;       // 存储的对象ID

        public QuadtreeNode(Quadtree root,float2 center, float2 size)
        {
            Root = root;
            Center = center;
            Size = size;
            
            Children = new QuadtreeNode[4];
            
            Objects = new HashSet<int>();
        }

        public bool Contains(float2 point)
        {
            var min = Center - Size * 0.5f;
            var max = Center + Size * 0.5f;
    
            return math.all(point >= min & point <= max);
        }

        public void Split()
        {
            var childSize = Size / 2;
            var offset = childSize / 2;

            foreach (var node in Children)
            {
                foreach (var id in Objects)
                {
                    var pos = Root.Positions[id];
                    if (node.Contains(pos))
                    {
                        node.Objects.Add(id);
                    }
                }
            }
            Objects.Clear();
            
            Children[0] = new QuadtreeNode(Root,Center + new float2(-offset.x, offset.y), childSize);
            Children[1] = new QuadtreeNode(Root,Center + new float2(offset.x, offset.y), childSize);
            Children[2] = new QuadtreeNode(Root,Center + new float2(-offset.x, -offset.y), childSize);
            Children[3] = new QuadtreeNode(Root,Center + new float2(offset.x, -offset.y), childSize);
        }
        
        public bool IsLeaf()
        {
            return Children[0].Size.x == 0; // 如果子节点未初始化，说明是叶子节点
        }
    }
}